The present application relates to a thin film transistor having an organic semiconductor layer and a method of manufacturing the thin film transistor, and an electronic apparatus in which the thin film transistor is used.
In recent years, thin film transistors (TFTs) have been used in a diversity of electronic apparatuses, as switching elements or the like. Recently, organic TFTs in which an organic semiconductor material is used for forming a semiconductor layer constituting a channel layer have come to be deemed as promising, in place of inorganic TFTs in which an inorganic semiconductor material is used for forming the semiconductor layer. This is because in the organic TFTs, the channel layer can be formed by a coating method and, therefore, a lowered cost can be ensured. A further reason resides in that, since the channel layer can thus be formed at a lower temperature than in a vapor deposition method or the like, a plastic film or the like which is flexible and low in thermal resistance can be used as a support substrate.
Together with the organic semiconductor layer forming the channel layer, an organic TFT has a source electrode and a drain electrode which are connected to the organic semiconductor layer. The source electrode and the drain electrode are formed from a metallic material or the like. The positional relationship that the source electrode and the drain electrode have with the organic semiconductor layer is classified into two types, of which commonly used is the top contact type wherein the source electrode and the drain electrode are so disposed as to be on the upper side of and to overlap with the organic semiconductor layer (see, for example, Japanese Patent Laid-Open No. 2008-085200).
In this type of organic TFT, the source electrode and the drain electrode formed of a metallic material are connected to the organic semiconductor layer formed of an organic material, so that the charge injection efficiency therebetween may be insufficient. In view of this, it has been proposed to form an organic conductive layer such as a hole injection layer on the organic semiconductor layer so that the organic conductive layer is provided intermediately between the source and drain electrodes and the organic semiconductor layer (see, for example, Japanese Patent Laid-Open No. 2006-253675 and Japanese Patent Laid-Open No. 2005-327797).